Methods and apparatus for fabricating gas turbine engines

ABSTRACT

Methods and apparatus of fabricating a gas turbine engine component are provided. The method includes selecting a surface of a component to apply a wear-resistant material, applying a formed wear pad fabricated from a wear-resistant alloy and a braze material, and vacuum brazing the component and applied wear pad wherein the wear-resistant alloy is bonded to the component surface using the braze material.

BACKGROUND OF THE INVENTION

This invention relates generally to turbine engines, and morespecifically to a method and apparatus for coupling a wear-resistantmaterial to a turbine engine component.

At least some known gas turbine engines include a forward fan, a coreengine, and a power turbine. The core engine includes at least onecompressor that provides pressurized air to a combustor wherein the airis mixed with fuel and ignited for generating hot combustion gases. Thecombustion gases flow downstream to one or more turbines that extractenergy therefrom to power the compressor and provide useful work, suchas powering an aircraft. A turbine section may include a stationaryturbine nozzle positioned at the outlet of the combustor for channelingcombustion gases into a turbine rotor disposed downstream thereof. Atleast some known turbine rotors include a plurality of circumferentiallyspaced apart turbine blades extending radially outwardly from a rotordisk that rotates about the centerline axis of the engine.

The turbine section also includes a shroud assembly coupled downstreamfrom the turbine nozzle. The shroud assembly circumscribes the turbinerotor and defines an outer boundary for the hot combustion gases flowingthrough the turbine. At least some known shroud assemblies include ashroud hanger member that is coupled to an outer casing of the engine toprovide support to a plurality of shrouds positioned adjacent to thetips of the high-pressure turbine blades. At least some known shroudhanger members include an axially forward flange that is positioned incompressive engagement to a mating surface on the circumferentiallyspaced apart nozzle segments.

The combination of differing rates of thermal expansion betweenadjacently coupled shroud hangers and turbine nozzle segments, thedynamic effects of the engine, for example, vibration and/or highcompression contact between shroud hangers and turbine nozzle segmentsmay result in wear of the shroud hanger at the interface. Over time, aworn surface may adversely affect turbine operating performance, and/orshorten the engine maintenance cycle-time. A wear-resistant coating,such as a thermal spray of a wear-resistant alloy, may be applied to theshroud hanger during fabrication to facilitate minimizing wear. However,such coatings may be susceptible to chipping, and a high level ofmanufacturing effort and cycle-time impact due to thermal sprayprocesses may result in relatively high manufacturing costs.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a method of fabricating a gas turbine enginecomponent is provided. The method includes selecting a surface of acomponent to apply a wear-resistant material, applying a formed wear padfabricated from a wear-resistant alloy and a braze material, and brazingthe component and applied wear pad wherein the wear-resistant alloy isbonded to the component surface using the braze material.

In another embodiment, a newly manufactured component is provided. Thecomponent includes a surface, and a wear-resistant material diffusionbonded to the surface using a wear pad that is pre-formed, the wear padincluding a sintered braze material powder and a wear-resistant alloypowder mixture, the wear-resistant material having a machined surfacethat defines a wear surface of the component, the wear-resistantmaterial including the braze material and the wear-resistant alloymixture.

In yet another embodiment, a gas turbine engine assembly is provided.The gas turbine engine assembly includes a compressor, a high-pressureturbine coupled to the compressor by a rotor shaft, and a shroudassembly at least partially circumscribing the turbine, the shroudassembly including a shroud hanger member having a forward face having asurface and a wear-resistant material applied to the surface using abrazing process, the wear-resistant material including wear-resistantmaterial including a mixture of between approximately 5% and 40% of abraze material, by weight and between approximately 60% and 95% of awear-resistant alloy material, by weight, the braze material including,by weight, between approximately 22.5% and 24.25% chromium, betweenapproximately 9.0% and 11.0% nickel, between approximately 6.5% and 7.5%tungsten, between approximately 3.0% and 4.0% tantalum, betweenapproximately 2.6% and 3.0% boron, the remainder including cobalt, minoralloying elements, and incidental impurities, the wear-resistant alloyincluding, by weight, between approximately 27% and 29% molybdenum,between approximately 16.5% and 17.5% chromium, between approximately3.0% and 3.5% silicon, less than approximately 3% iron, less thanapproximately 3% nickel, the remainder including cobalt, minor alloyingelements, and incidental impurities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an exemplary highbypass ratio turbofan engine;

FIG. 2 is a detailed partial sectional view of a portion of the gasturbine engine shown in FIG. 1;

FIG. 3 is a perspective view of an exemplary shroud hanger member thatmay be used with the gas turbine engine shown in FIGS. 1 and 2; and

FIG. 4 is a cross-sectional profile view of the shroud hanger membershown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “component” may include any componentconfigured to be coupled with a gas turbine engine that may be coatedwith a wear-resistant material, for example a turbine shroud hanger. Aturbine shroud hanger is intended as exemplary only, and thus is notintended to limit in any way the definition and/or meaning of the term“component”. Furthermore, although the invention is described herein inassociation with a gas turbine engine, and more specifically for usewith a turbine shroud hanger for a gas turbine engine, it should beunderstood that the present invention is applicable to other gas turbineengine stationary components and rotatable components. Accordingly,practice of the present invention is not limited to turbine shroudhangers for a gas turbine engine. In addition, although the invention isdescribed herein in association with a vacuum braze process, it shouldbe understood that the present invention may be applicable to anydiffusion joining process, for example, activated diffusion healing.Accordingly, practice of the present invention is not limited to vacuumbrazing.

FIG. 1 is a longitudinal cross-sectional view of an exemplary highbypass ratio turbofan engine 10. Engine 10 includes, in serial axialflow communication about a longitudinal centerline axis 12, a fan 14, abooster 16, a high-pressure compressor 18, a combustor 20, ahigh-pressure turbine 22, and a low-pressure turbine 24. High-pressureturbine 22 is drivingly connected to high-pressure compressor 18 with afirst rotor shaft 26, and low-pressure turbine 24 is drivingly connectedto booster 16 and fan 14 with a second rotor shaft 28.

During operation of engine 10, ambient air passes through fan 14,booster 16, and compressor 18, the compressed air stream enterscombustor 20 where it is mixed with fuel and burned to provide ahigh-energy stream of hot combustion gases. The high-energy gas streampasses through high-pressure turbine 22 to drive first rotor shaft 26.The gas stream passes through low-pressure turbine 24 to drive secondrotor shaft 28, fan 14, and booster 16. Spent combustion gases exit outof engine 10 through an exhaust duct (not shown).

It should be noted that although the present description is given interms of a turbofan aircraft engine, embodiments of the presentinvention may be applicable to any gas turbine engine power plant suchas that used for marine and industrial applications. The description ofthe engine shown in FIG. 1 is only illustrative of the type of engine towhich some embodiments of the present invention is applicable.

FIG. 2 is a detailed partial sectional view of a portion of gas turbineengine 10 (shown in FIG. 1). Combustor 20 includes an outer liner 202and an inner liner 204 that define an annular combustion chamber 206into which fuel is injected through a fuel nozzle 208 which extendsinwardly through combustion case 210. Combustor 20 is partially cooledby airflow from compressor 18 into an annular passageway 212 defined bycombustor outer liner 202 and combustion case 210. Similarly, on theinner side of combustor 20 an annular chamber 214 is defined by innerliner 204 and nozzle support structure 216 to cool that portion ofcombustor 20. Hot combustion gases, ignited and at least partiallyburned in combustor 20, flow rearwardly from combustion chamber 206 to arow of circumferentially spaced high-pressure nozzle segments 218, andthen further rearwardly to impinge on the circumferentially spaced rowof turbine blades 220 of high-pressure turbine 22. Circumscribing therow of high-pressure blades 220 in close clearance relationshiptherewith is an annular shroud 224. Shroud 224 may include a pluralityof annular sectors attached at an inner side of a shroud hanger member226 that is formed of a plurality of sectors that form a completecircle. Structural support for shroud 224 is provided by shroud hangermember 226 having at its rearward end a radially inwardly extending hook228, which is coupled to shroud 224 by a U-shaped bracket 230. A forwardend of shroud 224 is coupled to shroud hanger member 226 by a rearwardlyextending collar 232.

A forward face 234 of collar 232 is in high compression contact with arearward face 236 of a radially outward band 238 of high-pressureturbine nozzle segment 218. Forward face 234 and rearward face 236define a boundary between cooling air from compressor 18 and combustiongases from combustor 20. The temperature of the cooling air fromcompressor 18 and the temperature of the combustion gases from combustor20 may be variable with engine speed wherein different rates of thermalgrowth between collar 232 and high-pressure turbine nozzle segment 218may result in relative movement and variations in the compressive forcesbetween forward face 234 and rearward face 236. Such relative movementmay cause wear damage to shroud hanger member 226 and high-pressureturbine nozzle segment 218.

FIG. 3 is a perspective view of an exemplary shroud hanger member 226that may be used with gas turbine engine 10 (shown in FIGS. 1 and 2).Shroud hanger member 226 includes a forward flange 302 that includes aforward sealing lip 304 and forward face 234. Forward face 234 isconfigured for relatively high compression contact with outer band 238of nozzle segment 218. Forward face 234 may slidingly move with respectto outer band 238, such that the combination of high compression forceand relative movement between the contacting surfaces as a result ofmanufacturing tolerances, differing rates of thermal expansion, anddynamic effects during operation of the engine, over time may result inexcessive wear of these surfaces.

A wear-resistant pad 306 may be applied to forward face 234 tofacilitate reducing damage due to wear. In the exemplary embodiment,wear-resistant pad 306 is fabricated from a powder of metal or metalalloys with predetermined wear-resistant qualities. The powder ofwear-resistant metal or alloy may be mixed with a braze material, formedto dimensions complementary to forward face 234, and pre-sintered toadhere the powder and braze material to maintain the formed dimensionsof wear-resistant pad 306. In an alternative embodiment, wear-resistantpad 306 may be malleably formed to forward face 234.

Wear-resistant pad 306 may comprise a slurry mixture of braze powder,wear material powder, and a binder, for example, water-based organicmaterials such as polyethylene oxide and various acrylics, orsolvent-based binders. The slurry mixture may be cast to form a greentape wear material or the green tape may be sintered to form apre-formed and/or formable wear pad, such as wear-resistant pad 306. Useof the braze slurry compositions is advantageous in various situations.For example, when the final substrate surface is irregular, or containspits or crevices, the braze slurry can be used to fill such regions.

In an alternative embodiment, the braze slurry composition can beapplied to the surface region of the tape which will contact the desiredregion of the substrate. In another alternative embodiment, the brazeslurry composition is applied to both the wear material green tape andthe substrate region, which will be in contact with the tape.

The braze material may include a base constituent that is the same asthe wear-resistant alloy, but with a lower melting temperature than thewear-resistant alloy. In the exemplary embodiment, the braze material isa cobalt-base alloy comprising, by weight, between approximately 22.5and 24.25% chromium, between approximately 9.0 and 11.0% nickel, betweenapproximately 6.5 and 7.5% tungsten, between approximately 3.0 and 4.0%tantalum, between approximately 2.6 and 3.0% boron, with the remaindercomprising cobalt and minor or incidental elements such as carbon,zirconium, iron, silicon, manganese, copper, oxygen, nitrogen, selenium,phosphorus, and/or sulfur. A preferred nominal composition for the brazematerial is, by weight, approximately 23% chromium, approximately 10%nickel, approximately 7% tungsten, approximately 3.5% tantalum, andapproximately 2.8% boron, with the remainder comprising cobalt andincidental impurities.

In the exemplary embodiment, the wear-resistant alloy is a cobalt-basealloy comprising, by weight, between approximately 27% and approximately30% molybdenum, between approximately 16.5% and approximately 18.5%chromium, between approximately 3.0 and approximately 3.8% silicon, lessthan approximately 1.5% iron, less than approximately 1.5% nickel, lessthan approximately 0.03% sulfur, less than approximately 0.03%phosphorus, and less than approximately 0.08% carbon, with the remaindercomprising cobalt and incidental impurities.

During fabrication, a powder of wear-resistant alloy and a powder ofbraze material are blended to form a powder mixture comprising betweenapproximately 70% and 90% of the wear-resistant alloy, by weight, andthe remainder comprising braze material. In the exemplary embodiment,the powder mixture comprises between approximately 79% and 81%, byweight, of the wear-resistant alloy and the remainder comprising brazematerial. In the exemplary embodiment, the braze material in thewear-resistant alloy matrix is uniformly dispersed. In an alternativeembodiment, the braze material and the wear-resistant alloy are formedof alternating layers of the braze material and the wear-resistantalloy, such that, layers of the braze material are thinner than layersof the wear-resistant alloy.

The powder mixture may be formed into a pad of perdetermined dimensions.A polymeric or organic binder may be used to facilitate the bindingprocess and is capable of burning off at a temperature of not higherthan approximately 1200° F. (approximately 649° C.) to leave noundesirable residues. The formed pad may be sintered or partiallysintered at a temperature sufficient to fuse (agglomerate) the powderparticles and burn off the binder (e.g., between approximately 200° C.and 425° C.). A final dimension may be achieved using a waterjet, laseror other suitable technique.

Wear-resistant pad 306 may be brazed, such as vacuum brazed, to forwardface 234 of shroud hanger member 226 and then vacuum heat treatedfollowed by aging. Wear-resistant pad 306 may be coupled to forward face234 by a resistant welding method, for example, tack welding, or byadhesive. The braze process may be performed at a temperature of betweenapproximately 2100° F. and 2300° F. (between approximately 1150° C. and1260° C.) for between approximately ten minutes and sixty minutes. Forexample, at a temperature of between approximately 2195° F. andapproximately 2225° F. (between approximately 1202° C. and approximately1218° C.) for between approximately ten to twenty minutes in a vacuum ofless than 1×10−3 torr (less than 1.3×10−3 mbar). In the exemplaryembodiment, after the braze process, wear-resistant pad 306 may beinspected to ensure wear-resistant pad 306 has flowed smoothly andevenly on forward face 234 with a linear shrinkage of less than 5% and athickness shrinkage of less than 20%, such that a wear-resistantmaterial on forward face 234 is formed.

FIG. 4 is a cross-sectional profile view of shroud hanger member 226(shown in FIG. 3). A wear-resistant material 402 is formed from thebrazing of wear-resistant pad 306 to forward face 234. In the exemplaryembodiment, bonding between wear-resistant material 402 and forward face234 is at least 90% and a porosity of wear-resistant material 402 isless than approximately 4% by volume, with the major axis of any porenot exceeding 0.008 inches (approximately 0.2 mm) when measured bymetallographic evaluation at 100×, and a maximum of one inclusion beingpresent in any field of view examined at 50× magnification.

Wear-resistant material 402 may be aged to further bond a diffusion area404 to forward face 234 at a temperature of between approximately 2000°F. and 2100° F. (between approximately 1090° C. and 1150° C.) forbetween approximately one hour and four hours. Other heat treatmentsteps may also be applied based on the type of metal shroud hangermember 226 is fabricated from, or to support other manufacturingprocesses. Shroud hanger member 226 then may be final machined topredetermined dimensions.

The above-described methods and apparatus are cost-effective and highlyreliable for providing a wear-resistant material to newly manufacturedcomponents using a pre-formed sintered mixture of braze material powderand wear-resistant metal alloy powder, for example, in a pre-formedsintered composition. The methods and apparatus facilitate fabrication,assembly, and reduce the maintenance cycle-time of machines, and inparticular gas turbine engines, in a cost-effective and reliable manner.

Exemplary embodiments of wear-resistant material methods and apparatuscomponents are described above in detail. The components are not limitedto the specific embodiments described herein, but rather, components ofeach apparatus may be utilized independently and separately from othercomponents described herein. Each wear-resistant material method andapparatus component can also be used in combination with otherwear-resistant material method and apparatus components.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1-4. (canceled)
 5. A method in accordance with claim 0 wherein applyinga wear resistant material comprises: alternately layering a braze layerand a wear-resistant alloy layer; forming the wear pad to predetermineddimensions; and sintering the wear pad to facilitate fusing the powderparticles.
 6. A method in accordance with claim 0 wherein applying awear resistant material comprises blending the braze material powder andthe wear-resistant alloy powder to form a substantially uniformlydispersed mixture.
 7. A method in accordance with claim 0 whereinblending the braze material powder and the wear-resistant alloy powderto form a substantially uniformly dispersed mixture comprises blendingbetween approximately 5% and 40% braze material, by weight and betweenapproximately 60% and 95% wear-resistant alloy, by weight.
 8. A methodin accordance with claim 6 wherein blending the braze material powderand the wear-resistant alloy powder to form a substantially uniformlydispersed mixture comprises, blending between approximately 19% and 21%,by weight, of braze material powder and between approximately 79% and81%, by weight, of wear-resistant alloy powder.
 9. A method inaccordance with claim 7 wherein blending a braze material powder and awear-resistant alloy powder further comprises: forming the wear pad topredetermined dimensions; and sintering the formed wear pad to fuse thepowder particles. 10-12. (canceled)
 13. A newly manufactured componentcomprising: a surface; and a wear-resistant material diffusion bonded tosaid surface using at least one of a wear pad that is pre-formed, aslurry, and a green tape, said wear-resistant material comprising abraze material powder and a wear-resistant alloy powder mixture, saidwear-resistant material having a machined surface that defines a wearsurface of said component, said wear-resistant material comprising saidbraze material and said wear-resistant alloy mixture.
 14. A newlymanufactured component in accordance with claim 0 wherein said surfacecomprises a wear surface on a flange of a turbomachine shroud hangermember, said flange configured to support a shroud component of aturbomachine.
 15. A newly manufactured component in accordance withclaim 0 wherein said wear-resistant material comprises betweenapproximately 5% and 40% braze material, by weight and betweenapproximately 60% and 95% wear-resistant alloy, by weight.
 16. A newlymanufactured component in accordance with claim 0 wherein saidwear-resistant material comprises between approximately 19% and 21%braze material, by weight and between approximately 79% and 81%wear-resistant alloy, by weight.
 17. A newly manufactured component inaccordance with claim 0 wherein said braze material comprises, byweight, between approximately 22.5% and 24.25% chromium, betweenapproximately 9.0% and 11.0% nickel, between approximately 6.5% and 7.5%tungsten, between approximately 3.0% and 4.0% tantalum, betweenapproximately 2.6% and 3.0% boron, the remainder comprising cobalt,minor alloying elements, and incidental impurities.
 18. A newlymanufactured component in accordance with claim 0 wherein saidwear-resistant alloy comprises, by weight, between approximately 27% and29% molybdenum, between approximately 16.5% and 17.5% chromium, betweenapproximately 3.0% and 3.5% silicon, less than approximately 3% iron,less than approximately 3% nickel, the remainder comprising cobalt,minor alloying elements, and incidental impurities.
 19. A gas turbineengine turbine assembly comprising: a compressor; a high-pressureturbine coupled to said compressor by a rotor shaft; and a shroudassembly at least partially circumscribing said turbine, said shroudassembly comprising a shroud hanger member having a forward face havinga surface and a wear-resistant material applied to said surface using avacuum brazing process, said wear-resistant material comprising amixture of between approximately 5% and 40% of a braze material, byweight and between approximately 60% and 95% of a wear-resistant alloymaterial, by weight, said braze material comprising, by weight, betweenapproximately 20.0% and 25.0% chromium, between approximately 8.0% and12.0% nickel, between approximately 5.0% and 9.0% tungsten, betweenapproximately 2.0% and 5.0% tantalum, between approximately 1.5% and5.0% boron, the remainder comprising cobalt, minor alloying elements,and incidental impurities, said wear-resistant alloy comprising, byweight, between approximately 25% and 30% molybdenum, betweenapproximately 15.0% and 20.0% chromium, between approximately 2.0% and4.0% silicon, less than approximately 4.0% iron, less than approximately4.0% nickel, the remainder comprising cobalt, minor alloying elements,and incidental impurities.
 20. A gas turbine engine turbine assembly inaccordance with claim 18 wherein said wear-resistant material comprisesa mixture of between approximately 19% and 21% of a braze material, byweight and between approximately 79% and 81% of a wear-resistant alloymaterial, by weight, said braze material comprising, by weight, betweenapproximately 22.5% and 24.25% chromium, between approximately 9.0% and11.0% nickel, between approximately 6.5% and 7.5% tungsten, betweenapproximately 3.0% and 4.0% tantalum, between approximately 2.6% and3.0% boron, the remainder comprising cobalt, minor alloying elements,and incidental impurities, said wear-resistant alloy comprising, byweight, between approximately 27% and 29% molybdenum, betweenapproximately 16.5% and 17.5% chromium, between approximately 3.0% and3.5% silicon, less than approximately 3% iron, less than approximately3% nickel, the remainder comprising cobalt, minor alloying elements, andincidental impurities.